JP4970891B2 - Developer housing with allowable mass variation in reservoir - Google Patents

Description

  The present invention relates generally to the development of electrostatic latent images, and more particularly to a developer having a developer housing with increased tolerance for mass variations in the reservoir.

  In an electrostatographic printing process, the photoconductive surface is generally charged by charging it to a substantially uniform potential, and then photoconductive by activated radiation having a pattern corresponding to the desired image. The charge on the surface is selectively dissipated and developed by bringing the developing material into contact with the remaining charged pattern, ie, the electrostatic latent image, and the toner powder image formed by this development is copied from the photoconductive surface to the copy sheet. The image is formed by transferring the toner image onto the copy sheet and finally fixing the powder image on the copy sheet.

  Development materials that are commonly used in such processes include two-component development materials and one-component development materials. In general, a two-component developing material such as a two-component toner is composed of magnetic carrier fine particles and toner particles adsorbed thereto by triboelectricity, and a one-component developing material such as a one-component toner is charged with an electrostatic charge and therefore on the photoconductive surface. Toner particles that can be attracted and attracted to the latent image of the toner.

  Furthermore, a system for depositing toner particles on a latent image on a photoconductive surface is called a development system. Among the various known development systems, in a one-component development system, a donor roll is used as a means for transferring charged toner. The donor roll is positioned such that a development nip is formed between the donor roll and the photoconductive surface and is used to feed charged toner into the development nip. When developing the latent image recorded on the photoconductive surface with this toner, a mechanical scavengeless development system can be used in combination. The scavengeless one-component development system is a system in which a plurality of wire electrodes are provided in a development region so as to be adjacent to a donor roll at a small interval, and a toner is obtained when an AC voltage is applied to these wire electrodes. Is peeled off from the donor roll, and a toner powder cloud is formed in the development region. The electrostatic field generated in the latent image acts on the toner powder cloud, and as a result, the latent image is developed by the toner sucked from the toner powder cloud.

  In addition to the scavengeless development system, a developer material composed of carrier beads (carrier fine particles) and toner particles is magnetically attracted and adsorbed from a reservoir (developer material reservoir in the developer housing) to a magnetic developing roll (pickup). There is also a two-component development system in which toner particles are sucked and adsorbed from carrier beads on a magnetic developing roll to a donor roll, and the toner particles are conveyed to the vicinity of the latent image by the donor roll.

US Pat. No. 6,546,225 (B2)

  In such a two-component developing system, it is necessary to form a developing material layer having a uniform thickness on the developing roll. To do this, the effects of mass variations in the reservoir, machine tilt, toner concentration, environmental conditions, etc. must be overcome. For this reason, a mechanism that has been conventionally employed is a mechanism in which the pick-up amount by the above-described magnetic pickup is made considerably larger than the required amount, and excess development material is removed by trimming. According to this method, the amount of the developing material on the developing roll can be set to an amount sufficient for forming the entire surface of the magnetic brush, even within a limited range in which conflicting conditions are satisfied. On the other hand, with this mechanism, a considerable amount (for example, an amount that is probably as high as 80% under the reference condition) of the development material first captured on the development roll is removed by trimming. In general, in combination with the fact that the magnetic field for pick-up is extremely strong, in the two-component development system based on such a mechanism, the surface of the developing roll is extremely worn, the life of the developing material is short, and the energy is wasted. There was a problem.

  Therefore, regarding the configuration of the developing device and its housing, it is possible to make the size of the developing material flow or the amount of developing material flowing into the developing region (for example, the developing nip between the magnetic developing roll and the donor roll) constant. In particular, even if the development material in the development material pool (mass in the pool) or volume (volume in the pool) fluctuates over a wide range compared to the range that can be dealt with by the conventional method, the development material for the development area is dealt with. It is desired that the flow (amount) can be made constant.

  Here, in the developing system according to an embodiment of the present invention, three types of augers, that is, an upper transfer auger, a mixing / pumping auger and a lower (for example, lower front) transfer auger, and an upper magnet are provided in the developer housing. Two types of magnetic developing rolls, which are a developing roll and a lower magnetic developing roll, are accommodated. During operation, the development material in the development material reservoir in the developer housing is pushed to the upper transfer auger side by the upper part formed by the mixing / pumping auger, and the development material picked up from the periphery of the upper transfer auger is used for development. Is done. The present embodiment further adopts a configuration in which when the developing material is supercharged to the upper part of the drawing, the excessive developing material can leak to the lower transfer auger side. By adopting such a configuration, in this embodiment, if the mass in the reservoir is above a certain lower limit value, the upper transfer is performed by the upper part of the mixing / pumping auger regardless of the mass in the reservoir or the volume in the reservoir. Since the amount of development material pushed into the auger is constant, the amount of development material that can be picked up from the periphery of the upper transfer auger is remarkably constant. If the amount of replenishment developing material that can be picked up is constant (under normal conditions), it is not necessary to enhance the pickup function, and therefore the magnetic field for pickup used may be low. If the magnetic field for pick-up is low, the mechanical power for driving the structure inside the developer housing including the magnetic structure for generating the magnetic field is small, and the life of the developing roll is extended. The amount is reduced. As described above, according to the developing system or the developing device housing according to the present embodiment, the developing material replenishing ability measured by an index such as MOR (mass on roll), MOS, or CPH (compressed pile height) is greater than the lower limit value. If there is a mass in the reservoir, it can be made constant against fluctuations in the mass in the reservoir, and power consumption, component wear and development material waste can be suppressed.

  Hereinafter, preferred embodiments of the present invention will be described. The following description is not an explanation intended to limit the present invention to the following embodiments, but rather various configurations in place of the following embodiments, various configurations corresponding to modified versions of the following embodiments, and the following embodiments. It is intended to cover various functionally equivalent structures and the like as long as they belong to the technical scope of the present invention defined by the appended claims and share the essence thereof. It is.

  Today, electrophotographic technology is already a well-known technology. Therefore, first, the configuration and functions of various processing stations in FIG. 1 will be briefly described with reference to FIG. 1 schematically showing the configuration of the electrophotographic printing machine.

  FIG. 1 shows an example of an electrophotographic printing machine in which a developing device according to an embodiment of the present invention is incorporated. The belt 10 used in the printing press has a configuration in which a photoconductive surface 12 is deposited on a conductive substrate. In the printing press, various processing stations are arranged along the belt 10. Thus, by advancing the belt 10, each part of the photoconductive surface 12 can be passed through various processing stations. As means for advancing the belt 10, a drive roll 22 on which the belt 10 is applied and a belt driving motor 24 connected to the roll 22 by a suitable material, for example, a drive belt, are provided. Therefore, by appropriately operating the motor 24, the roll 22 can be rotated in a desired direction, and the belt 10 can be advanced in the desired traveling direction 16 (arrow in the figure).

  The charging station A passes through each part of the belt 10 first. This station A is provided with a corona generator 26 and a high voltage power supply (HVPS) 28 connected thereto. When the portions of the photoconductive surface 12 of the belt 10 are sent to the charging station A, the corona generating device 26 charges the portions almost uniformly with a certain potential as a target (uniform charging process). The potential targeted by the uniform charging process is generally high, and such a high potential uniform charging process is executed using a power supply voltage supplied from the HVPS 28 to the corona generating device 26. The portion of the photoconductive surface 12 of the belt 10 that passes through the charging station A continues to the exposure station B.

  Although not shown, the exposure station B is provided with an exposure controller that receives and processes image signals from the print controller. The image signal supplied from the print controller is a signal indicating a desired output image, that is, an image to be printed, for example, a signal indicating an image read from the document 30 on the platen 32. The exposure controller converts the image signal into an output scanning signal by signal processing, and sends the signal obtained by the conversion to a laser-based output scanning device. The output scanning device outputs and scans laser light in accordance with a signal sent from the exposure controller, thereby discharging the charge holding surface, that is, the photoconductive surface 12 of the belt 10 in a site-selective manner. As this output scanning device, it is desirable to use a laser ROS (raster output scanner) 36 as shown in the figure, but other types of electrophotographic exposure devices such as LED arrays can also be used.

  The electrostatic latent image thus recorded on the photoconductive surface 12 by the exposure station B proceeds to the development station C as the belt 10 proceeds further. The development station C is provided with a development unit 38 for developing the recorded latent image on the photoconductive surface 12. As will be described later, the developing unit 38 has a configuration in which developing rolls 40 and 41 are mounted inside a chamber formed by the developing unit housing, and the developing rolls 40 and 41 are at least partially wrapped by the developing unit housing. is doing. The chamber in the developing device housing is also a developing material reservoir for storing a developing material for replenishment. The developing material to be used differs depending on the basic configuration of the printing machine, and may be a one-component developing material composed exclusively of charged toner particles, or a two-component or multi-component developing material containing at least toner particles and magnetic carrier fine particles. Sometimes it becomes.

  When the electrostatic latent image is developed, it becomes a toner powder image. The portion of the belt 10 where the development has been completed and the toner powder image is formed proceeds to the transfer station D as shown in FIG. The transfer station D is provided with a sheet feeding device 72 for feeding a copy sheet (for example, a paper sheet) 70 as a support base to the transfer station D. The sheet feeding device 72 preferably feeds the uppermost copy sheet 70 in the stack 76 into the chute 78 by the feeding roll 74 and feeds it to the transfer station D via the chute 78 to the photoconductive surface of the belt 10. 12 to be brought into contact. The timing at which the sheet 70 is brought into contact with the photoconductive surface 12 while being advanced is set or controlled so that the toner powder image formed on the photoconductive surface 12 by development is brought into contact with the sheet 70 at the transfer station D. To do. The transfer station D includes a corona generating device 80 for spraying ions on the back surface of the sheet 70, that is, the surface opposite to the toner powder image contact side, and the toner powder image on the photoconductive surface 12 by this ion spraying. Is sucked and transferred onto the sheet 70. The sheet 70 to which the toner powder image has been transferred in this manner is then conveyed in the direction of the arrow 82 by a conveyor (not shown) and sent to the fusing station E.

  The fusing station E includes a fuser assembly 84 that permanently fixes the toner powder image transferred onto the sheet 70 to the sheet 70. The fuser assembly 84 includes a high-temperature fuser roll 86 and a backup roll 88 opposite to the fuser roll 86, so that the sheet 70 passes between the fuser roll 86 and the backup roll 88, and at that time, the toner powder on the sheet 70. The body image is configured to come into contact with the fuser roll 86. The toner powder image is melted by heating by the fuser roll 86 or pressurization by the backup roll 88 and is permanently fixed to the sheet 70. After this fusion, the sheet 70 is sent to the catch tray 94 through the chute 92. The operator of the printing press can receive the sheet 70 sent to the catch tray 94.

  Immediately after separation from the copy sheet 70, some toner particles remain on the photoconductive surface 12 of the belt 10. This residual toner adhered to the photoconductive surface 12 is removed from the photoconductive surface 12 at the cleaning station F. In the cleaning station F, a rotating fiber brush 96 is mounted so as to be in contact with the photoconductive surface 12, and particles on the photoconductive surface 12 are photoconductive by contact with the brush 96 and rotation of the brush 96. It is removed from the surface 12. After cleaning, the photoconductive surface 12 is illuminated throughout by a discharge lamp (not shown). Any charge remaining on the photoconductive surface 12 is dissipated by this illumination. Thereafter, the same image forming cycle starting from the uniform charging process of the photoconductive surface 12 is repeatedly performed.

  The overall operation of the electrophotographic printer incorporating the developing device according to the embodiment of the present invention has been described to a sufficient extent in view of the gist of the present invention.

  Next, an embodiment of the present invention will be described in more detail with reference to FIG. The overall function of the developing unit 100 shown in FIG. 2 is formed on the image receptor, for example, on the photoconductive surface 12 of the belt 10 (only part of which is shown in FIG. 2) by site-selective charging or discharging. This is a function of depositing a developing material or marking material such as toner on the latent image. Such functions as a whole are conventionally known. Further, depending on the type of loading destination printing machine (electrophotographic printing machine, electrophotographic copying machine, etc.), a plurality of such developing units 100 may be mounted. For example, in a color printer or the like, one developing unit 100 may be mounted for each primary color.

  The developing unit 100 includes a developing device housing and a developing roll, as is usual in various developing units. Among the components of the developing unit 100 shown in FIGS. 2 and 3, the developing device housing 112 roughly functions as a developing material reservoir for holding a developing material for replenishment and variously mixes the developing material. It has a function of holding the augers 130, 132 and 134 which are members to be transferred. Among the constituent elements, magnetic developing rolls 136 and 138 provided as one form of the developing rolls 40 and 41 are developing members on which magnetic brushes are formed. The development material is transferred and applied upward.

  The magnetic developing rolls 136 and 138 in the present embodiment are substantially cylindrical as shown in the figure, and are members having relatively high rigidity. Fixed magnetic structures 110 and 111 are provided in the magnetic developing rolls 136 and 138, respectively. The magnetic structures 110 and 111 are designed to hold a position within the magnetic developing rolls 136 and 138 that rotate about their axes. The magnetic structures 110 and 111 are composed of several necessary magnetic members. These magnetic members can be configured as a collection of a plurality of single metal magnets. Also, a continuous surface like a plastic magnet is divided into a plurality of areas and each area is magnetized to a predetermined polarity. A configuration is also possible. Or it may be realized by an electromagnet. The purpose of providing such magnetic structures 110 and 111 in the magnetic developing rolls 136 and 138 is to guide the magnetic carrier fine particles from the developing material supply source to the surface of the magnetic developing rolls 136 and 138 and attract them by magnetic attraction (pickup). To provide functions. The fine magnetic carrier particles picked up by the magnetic developing rolls 136 and 138 in this pickup area proceed to the developing area through the trimming area as the magnetic developing rolls 136 and 138 rotate. When the developing unit 100 is configured as a two-component developing material using type developing unit, the basic operation of the magnetic developing rolls 136 and 138 is to make carrier fine particles (carrier beads) into magnetic structures 110, as well known in the electrophotographic field. The magnet is attracted by the magnet 111 and the magnetic brush filament group (usually iron iron or agglomerates) is formed on the roll surface, particularly around the magnetic poles fixed in the magnetic structures 110 and 111. It becomes. Since some toner particles are electrostatically attached to each carrier bead, the toner particles can be conveyed into the developing region by rotating a magnetic brush formed by attracting the carrier beads. In a two-component development system, the toner particles deposited on the formed magnetic brush are usually in direct contact with the photoconductive surface 12 of the belt 10, thereby developing the latent image on the photoconductive surface 12. The

  In this technical field, members such as a paddle, a scavengeless developing electrode, and a commutator are known as means for developing a latent image in addition to a developing roll such as a magnetic developing roll. In carrying out the present invention, such other types of developing members can also be used. In the illustrated embodiment, air manifolds 140 and 142 are also provided that are attached to an unillustrated vacuum source. These air manifolds 140 and 142 are used to remove contaminants and excess particles in the transfer area near the belt 10. In many development units, the above-described two-component development material is used. Of the toner particles and carrier fine particles that are components of the two-component developing material, the carrier fine particles normally do not adhere to the belt 10 and continue to circulate in the developing device housing 112.

  In the above-described trickle developing system (and a certain type of developing unit), a port is provided for letting out surplus or waste developing material of the developing device housing 112. That is the outlet 190 in the figure. There are many purposes for discharging the developer material through the outlet 190, one of which is to maintain the toner particle to carrier fines ratio and the mass in the reservoir in the developer housing 112 at a desired level. In the present embodiment, the outlet 190 is located near the auger 130 and communicates with the outlet pipe 150. Excess or waste developing material that has exited from the outlet 190 is transported to the discharge pipe 152 by the outlet pipe 150 and is transported to a discharge port (not shown) by the transport auger 154 in the discharge pipe 152.

  4 to 6 show the developing material flow path in the developing device housing 112 of the present embodiment in a topologically accurate manner with respect to FIG. 4 to 6 are topologically accurate, the relative positional relationship of each component from the inboard end to the outboard end of the developer housing 112, and the pickup, trimming, and handoff. In other words, the elements are omitted or modified so that the location of the various functions such as development can be understood from FIGS. Accordingly, FIGS. 4 to 6 do not accurately indicate the actual positions of various components or components. See FIG. 2 for such details.

  Of the three augers shown, the upper transfer auger 134 located in the auger channel 220 is the pick-up auger and the auger 130 located in the lower auger channel 224 is the mixing / pumping auger. The auger 132 located in the auger channel 226 below the auger 134 and before the auger 130 is a lower transfer auger for release. The upper transfer auger 134 is an unequal pitch auger in this example, but may be an unequal core size auger. A non-uniform pitch auger was filed at the same time as the present application, entitled “Electrophotographic development unit with unequal pitch auger”, and unequal core size auger “Electrophotographic development unit with unequal core size auger”. See each patent application entitled The contents of these applications are incorporated herein by this reference. Further, the developing material flow path (developing material transfer system) in the developing device housing 112 includes paths 201, 202, 204, 205, 206, 208 and 210. The portion near the outboard end of the mixing / pumping auger 130 constitutes the pumping upper part 200 together with the receiving auger channel 224, and the developing material in the pumping upper part 200 is routed 202 (upward arrow) by the pumping operation of the pumping upper part 200. The developer material that has been transferred to the portion close to the outboard end of the auger channel 220 is transferred over the entire length from the outboard end side to the inboard end side of the developer housing 112 by the upper transfer auger 134 in the auger channel 220. The developing material transferred along the path 204 and picked up from the upper transfer auger 134 by the upper developing roll 40 (upper magnetic developing roll 136) is the lower developing roll 41 (lower magnetic developing) of the roll 40 and the handoff destination. It is used for the development process by the roll 138, and further the path 201 (fine The development material that has not been picked up from the pick-up auger 134 and is not used for development is traced back to the auger channel 224 by following the path 206 (downward arrow). To do. The portion near the inboard end of the mixing / pumping auger 130 constitutes a mixing unit or transfer unit 203 together with the auger channel 224 of the accommodation destination, and the developing material returned into the auger channel 224 is mixed by the mixing / pumping auger 130. It is transferred from 203 to the upper part 200 along the path 208.

  The developer material flow in the lower part of the inner space of the developing device housing 112 includes an auger separation wall 146 that separates the mixing / pumping auger 130 from a lower transfer auger 132 in front of the mixing / pumping auger 130. There is an opening formed. The formation position of the outlet 145 in the auger separation wall 146 is near the boundary between the mixing unit 203 and the pumping unit 200, strictly, slightly closer to the mixing unit 203. This outlet 145 operates as an opening for decompression. That is, when a larger amount of developing material is likely to enter the upper drawing portion 200 than the amount that can be pumped by the upper drawing portion 200 to the upper transfer auger 134, the excess amount of the developing material is passed through this outlet 145 or the auger. Leaks into the auger channel 226 through the separation wall 146. The developer material flow along the path 210 merges with the developer material flow along the path 205 in the auger channel 226 transferred by the lower transfer auger 132 and the developer material flow released via the path 210 to be inboard. Near the edge, it rejoins the developer material flow along the path 208 in the auger channel 224.

  The mixing / pumping auger 130 has several functions including the functions (a) to (d) described below. That is, the mixing / pumping auger 130 (a) transfers the development material from the inboard end to the outboard end along the path 208 shown in FIG. 4 and (b) replenishes the portion near the inboard end via the path 205. The supplied developing material (toner particles and magnetic carrier fine particles) is mixed and stirred with the developing material in the auger channel 224, (c) the developing material is pumped up (pushed up) to the upper transfer auger 134, and (d) the developing material. It has various functions of acting as a mass or volume buffer that absorbs fluctuations in the amount of development material stored in the reservoir (mass in reservoir or volume in reservoir). The P / D ratio (pitch to diameter ratio) of the mixing / pumping auger 130 in the pumping portion 200, that is, the value obtained by dividing the blade pitch by the core diameter is relative to the P / D ratio of the mixing / pumping auger 130 in the mixing unit 203. The former part is preferably designed to be an integer multiple of 2 with respect to the latter so that the mixing part 203> the upper part 200 is satisfied. Accordingly, the developing material transfer speed in the auger channel 224 is higher in the mixing unit 203 than in the pumping unit 200, and the volume flow rate is higher in the mixing unit 203 than in the pumping unit 200 if the cross-section filling rate is the same. The “development material transfer speed” is the displacement of the development material per unit time expressed in units of mm / sec or mm / auger rotation, and the “cross-section filling rate” is the development material of the auger channel cross section. The cross-sectional area of the filled part (filling cross-sectional area) is the ratio of the auger cross-sectional area, its blade partial cross-sectional area, or auger channel cross-sectional area. “Volume flow velocity” passes through the virtual plane during unit time. This is the volume of the developing material to be processed. The volume flow rate in the auger is equal to the filling cross-sectional area of the auger or auger channel multiplied by the developer feed rate.

  Therefore, when the P / D ratio in the mixing unit 203 is twice the P / D ratio in the pumping unit 200, the developing material transfer speed in the mixing unit 203 is the development in the pumping unit 200 if the cross-section filling rate or the volume filling rate is equal. Since the material transfer speed is doubled, when the inside of the pump top 200 is full, the full state inside the pump top 200 is maintained only by filling the mixing unit 203 to about half the filling rate. can do. Even if the amount of the developing material fed into the pumping portion 200 is further increased, leakage into the auger channel 226 occurs, so that the amount of the developing material pumped up to the upper transfer auger 134 by the pumping portion 200 does not change. According to the knowledge of the applicant of the present application, if the P / D ratio is 0, the development material transfer speed is also 0. However, if the P / D ratio exceeds a certain upper limit value, the development material transfer speed decreases. This is because when the P / D ratio exceeds the upper limit value, the efficiency of the rotation of the developing material around the auger shaft is impaired, and it begins to show signs that the rotation stops. Applicants have clarified that this upper limit is 1.2, so the range of P / D ratios available for mixing and transfer is about 0.2 to 1.2, preferably 0.8 to 1. It can be said that it is 1. It should be noted that the P / D ratio in the mixing unit 203 and the P / D ratio in the drawing portion 200 may be changed stepwise or continuously.

  Of the developing materials in the developing material reservoir 112 of the developing device housing 112, the amount of developing material in the pumping upper portion 200 is at most the full amount determined by the amount of developing material that can be pumped from the upper pumping portion 200 to the upper transfer auger 134. It remains at (the amount that fills the top of the pump 200). Among the developing materials in the developing material reservoir, developing materials other than those in the pumping unit 200 are in the mixing unit 203 or the auger channel 226, and these developing materials are sent to the pumping unit 200 by the mixing unit 203. Will be. As long as the inside of the pump top 200 is not full, the amount of the development material in the pump top 200 can be increased by the developer material fed in this way. Even if the development material is fed by the section 203, the amount of development material in the upper part 200 no longer increases. The excessive amount of developer material that cannot be pumped up by the pumping upper part 200 overflows the so-called mixing unit 203 and enters the auger channel 226 that accommodates the lower transfer auger 132 through the outlet 145. The route 210 in FIG. 5 is this route.

  The lower front transfer auger 132 transfers the development material flowing from the mixing / pumping auger 130 side through the outlet 145 while transferring the development material along the path 205 from the outboard end toward the inboard end. In addition, the developing material is received from the lower developing roll 41 evenly in the longitudinal direction. These development materials are fed into the mixing / pumping auger 130 when they reach the inboard end.

  Next, in order to make the above description regarding each system component and the cooperation thereof easier to understand, a developing material replenishment procedure for the developing unit 100 will be described. Initially, the developer housing 112 is empty. When the developing unit 100 is used, the developing material is poured (slowly) into the empty developing device housing 112. Then, the developing material accumulates (slowly) in the developing device housing 112. As the developer material is poured, the mass level (mass in the reservoir) to the volume level (volume in the reservoir) in the developer material reservoir increases, and eventually the inside of the pump top 200 becomes full.

  Immediately after the pumping top 200 is full, (A) there is no overflow of the developing material to the lower transfer auger 132 side via the outlet 145, and (B) the pumping top 200 is, for example, 50% full (C) The pumping capacity of the upper pumping part 200 is used to the maximum extent. That is, as shown in FIG. 6, the drawing portion 200 is full, and the densely packed development material is transferred by the drawing portion 200 at the development material transfer speed upper limit value. When further developing material is added to the developing device housing 112 from this state, the amount (level) of the developing material in the mixing unit 203 increases due to the increase in the mass in the pool or the volume in the pool, and (2) by the mixing unit 203. The surplus of the developer material that has been transferred leaks through the outlet 145, and (3) the filling rate of the auger channel 226 in which the lower-side transfer auger 132 is housed increases.

  However, since the drawing portion 200 has already drawn up to its full capacity, the amount of the developing material fed to the upper transfer auger 134 side and the amount of the developing material supplied to the pickup area of the magnetic developing roll 136. Furthermore, no change occurs in the MOR of the magnetic developing roll 136 after trimming. The replenishment of the developing material into the developing device housing 112 can be performed without affecting the MOR until the developing device housing 112 overflows with the developing material. FIG. 7 shows by experimental data that the MOR hardly changes even when the mass in the reservoir is increased. When the developing material mass or volume in the developer housing 112 is increased, finally, the filling rate of the auger channel 226 in which the lower transfer auger 132 is accommodated reaches 100%, or the mixing / When the filling rate of the mixing unit 203 related to the pumping auger 130 reaches 100%, the development material cannot be increased any more (overflowed state). Preferably, this situation is reached after the developer material amount has increased by about 50% after the developer material has started to leak through the outlet 145. Therefore, according to the developing unit 100, as long as the mass in the reservoir reaches the lower limit value, the MOR related to the development material is kept constant even if the mass in the reservoir or the volume in the reservoir changes considerably. In addition, as long as there is a sufficient amount of developer material in the developer housing 112 to keep the pumping top 200 receiving portion full (and excess developer material leaks from the outlet 145), the same behavior will occur. Even if the inclination of the developing device housing 112 changes, the MOR is kept constant.

  Thus, as is apparent from the above description, according to the present invention, it is possible to provide an auger that can achieve all of the above-described objects and can realize all of the above-described effects. In addition, the above description has been a description of a specific embodiment of the present invention. As is clear from this description, if the person skilled in the art (a so-called person skilled in the art) is skilled in the art, the embodiment will be described based on the disclosure of the present application. Can be modified as appropriate, many alternatives can be devised, and improvements can be made if necessary. Such modifications, alternatives and improvements are also encompassed in the technical scope and spirit of the present invention as defined by the appended claims.

1 is a schematic elevation view showing an example of an electrostatographic printing machine including a developing unit incorporating a characteristic configuration according to an embodiment of the present invention. FIG. 2 is a schematic elevation view showing an example of a developing unit that can be used in the printing machine shown in FIG. 1. FIG. 4 is a diagram illustrating a part of a developing unit according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a developing material flow path in the developing unit shown in FIG. 2. FIG. 3 is a diagram illustrating a developing material flow path in the developing unit shown in FIG. 2. FIG. 3 is a side view illustrating a developing material flow path in an auger 130 in the developing unit shown in FIG. 2. It is a graph which shows experimental data.

Explanation of symbols

  38,100 Developing unit, 40, 41 Developing roll, 112 Developing device housing, 130, 132, 134 Auger, 136,138 Magnetic developing roll, 145 outlet, 200-upper part, 201, 202, 204, 205, 206, 208 , 210 development material flow path, 203 mixing section, 220, 224, 226 auger channel, C development station.

Claims (3)

A developing device housing having a developing material reservoir that can store up to a predetermined amount of the developing material, and a development that is rotatably mounted in the developing device housing and transfers toner particles in the developing material to a latent image on the photoconductive member in the developing region. A member and a transfer system for transferring the development material from the development material reservoir to the development member,
A transport system is disposed adjacent to the mixing / pumping auger and a mixing / pumping auger that transports the developer material while mixing along a first path through the first auger channel of the storage destination. A lower transfer auger for transferring the development material along a second path passing through the two auger channels, a wall member disposed between the mixing / pumping auger and the lower transfer auger, and the mixing / pumping auger An upper transfer auger that supplies the developing material pumped up by the developing member ,
Further, the wall member is formed with an opening serving as an outlet from the first path to the second path at a position adjacent to the upper part of the pump where the mixing / pumping auger pushes up the development material toward the upper transfer auger. When the developer material volume in the upper part of the pump is substantially full, the excess developer material is recirculated through this outlet,
The mixing / pumping auger transfers the developing material at a first speed in the mixing portion located upstream of the pumping portion with respect to the developing material transfer direction in the first auger channel, while the first auger Designed to transport developer material at a second speed at the top of the channel, wherein the first speed is such that the mixing portion of the first auger channel or the second auger channel is full of developer material Is set to be greater than the second speed so as to keep the upper part of the first auger channel filled with the developing material even when not
Development system for electrophotographic printers. The development system for an electrophotographic printing machine according to claim 1,
The mixing / pumping auger has a first blade pitch diameter ratio in the mixing section, the a second blade pitch-diameter ratio at pumping unit, said first blade pitch diameter ratio is the second blade pitch diameter ratio Greater than the development system. The development system for an electrophotographic printing machine according to claim 2,
The development system, wherein the first blade pitch diameter ratio is twice the second blade pitch diameter ratio.

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